WASHINGTON — Representatives of labor, large corporations and the insurance industry have formed the first major coalition to publicly oppose the Clinton Administration on health care reform.

The group, calling itself the Coalition to Preserve Health Benefits, is planning an orchestrated campaign against an expected part of the emerging Administration reform plan: taxation of health care benefits.

"This is a White House that can't get it right on choosing an attorney general. Why should we think they will get it right on health care, which is infinitely more complicated?" said Kenneth Feltman, executive director of the Employers Council on Flexible Compensation, whose board includes Citicorp, TRW, Hughes Aircraft, Kraft General Foods and Pepsico.

Feltman's organization, along with the AFL-CIO and a group of small and medium-sized insurance firms, have scheduled a press conference today to unveil their campaign. The coalition plans rallies in six cities, beginning in Austin, Tex., on Thursday, to drum up support for its cause.

By creating a standard national package of health benefits worth $2,500 to $3,000 and taxing any benefits above that level, the Administration would pit workers against companies and cripple a firm's ability to determine the best health care coverage for its employees, Feltman said Monday.

According to a senior member of the White House Task Force on National Health Care Reform, such a concept is "very much a part of (health care reform) discussions" and is being pushed vigorously by champions of managed competition.

Another White House official confirmed Monday that taxation of benefits through managed competition is "definitely on the table."

The Clinton Administration is attempting to develop a basic benefits package for all Americans under a program of universal health insurance coverage. Likely to be a bare-bones package, given the costs, it would emphasize preventive and primary care, while including some level of hospital coverage, senior task force officials said.

Advocates of managed competition, who include some of Clinton's closest advisers on the health issue, argue that a tax on benefits has two advantages.

It would raise billions of dollars desperately needed to help pay the cost of basic coverage for 36 million Americans who now lack health insurance.

And it would force workers and employers to choose less costly benefits packages.